The present invention relates to linear motors of the type including two parallel ferromagnetic plates with a coil positioned between them. When the coil is energized, a linear movement is produced by the interaction of the energized coil and the magnetic flux from the ferromagnetic plates. The coil may be a single phase or polyphase winding and the ferromagnetic plates may generate the magnetic field by permanent magnets or by electromagnetic induction.
The winding according to the linear motor of this invention contains no permeable material. As such, it is `slotless` or `ironless` and has the advantage of very light weight and zero cogging. Several motors of this general type are known including motors disclosed by von der Heide (U.S. Pat. No. 4,151,447) who discloses the general construction and advantages of such linear motors, Chitayat (U.S. Pat. No. 4,749,921) who discloses an improved construction method and the addition of cooling, and Beakley (U.S. Pat. No. Re 34,674) who discloses an alternate construction with overlapping coils.
In motors of this type the coil is typically molded in epoxy and/or retained by a non-magnetic plate (such as in Chitayat) which provides a convenient means of positioning and mechanically retaining the coil between the ferromagnetic plates.
Although this type of ironless linear motor has been in existence for some time, very little has been done to optimize the coil pattern in order to improve performance. Having no slots to constrain the coil, complete freedom exists to adjust the coil windings to almost any pattern that is of advantage for performance or manufacturing benefits.
It is significant to note, for example, that Beakley teaches that the coil is substantially perpendicular to the longitudinal axis of the ferromagnetic plate (perpendicular to the direction of motion) and Chitayat teaches that the coil contains substantially straight runs. While it is conventional to consider that straight coils perpendicular to the longitudinal axis produce the maximum force, it is not always advantageous to use such a construction, particularly in a linear motor where motor heating is of concern.